13:45 〜 14:00
[J05-5-02] Crustal deformation process in Mid-Niigata as observed by dense GPS network before and after the 2011 Tohoku-oki earthquake
The Niigata-Kobe Tectonic Zone (NKTZ) is a deformation zone along the east coast of Japan Sea, with localized E-W contraction (Sagiya et al. 2000). Meneses-Gutierrez and Sagiya (2016) studied strain rate distributions based on GPS data from GEONET in central Japan before and after the Tohoku-oki earthquake and found persistent localized contraction (4-10x10-8/yr), in northern NKTZ, showing that the concentrated contraction is mainly inelastic in the form of aseismic fault slip. However, complete scale characterization of the deformation source was not possible due to limited spatial resolution of the GPS data.
In 2010, the Association for the Development of Earthquake Prediction in collaboration with Nagoya University, constructed 20 continuous GPS sites in Mid-Niigata. Analysis of this network with GEONET allows a better description of the deformation source in the area. We evaluate the Mid-Niigata response during the preseismic (2008-2011) and postseismic period (2013-2016) of the Tohoku-oki earthquake. We calculate horizontal strain rate distributions from the displacement rate data using Shen et al.'s method (1996), with a 15km distance decay constant. Then, we decompose the E-W strain rate with respect to its wavelength following Meneses-Gutierrez and Sagiya (2016). We found persistent localized contraction in the short wavelength component within 40 km before and after the quake. However, differences in the amplitude and horizontal location of the localized deformation suggested that elastic heterogeneities of the crust, acting in different sense before and after the event, might affect the deformation. We modeled the deformation in the preseismic and postseismic period considering an aseismic fault and an elastic heterogeneity as the source of deformation. We found that a fault cutting the whole crust at an angle of 30-40º with a slip rate >10mm/yr and an elastic heterogeneity with horizontal width of 60km located above the fault can explain the deformation.
In 2010, the Association for the Development of Earthquake Prediction in collaboration with Nagoya University, constructed 20 continuous GPS sites in Mid-Niigata. Analysis of this network with GEONET allows a better description of the deformation source in the area. We evaluate the Mid-Niigata response during the preseismic (2008-2011) and postseismic period (2013-2016) of the Tohoku-oki earthquake. We calculate horizontal strain rate distributions from the displacement rate data using Shen et al.'s method (1996), with a 15km distance decay constant. Then, we decompose the E-W strain rate with respect to its wavelength following Meneses-Gutierrez and Sagiya (2016). We found persistent localized contraction in the short wavelength component within 40 km before and after the quake. However, differences in the amplitude and horizontal location of the localized deformation suggested that elastic heterogeneities of the crust, acting in different sense before and after the event, might affect the deformation. We modeled the deformation in the preseismic and postseismic period considering an aseismic fault and an elastic heterogeneity as the source of deformation. We found that a fault cutting the whole crust at an angle of 30-40º with a slip rate >10mm/yr and an elastic heterogeneity with horizontal width of 60km located above the fault can explain the deformation.